How the RMD is figured
A required minimum distribution is arithmetic, not judgment: take the account's value on December 31 of the previous year and divide it by the "applicable denominator" next to your age in the IRS Uniform Lifetime Table (Table III in Publication 590-B). The age is the one you reach on your birthday in the distribution year. At 73 the denominator is 26.5, so a $400,000 IRA requires about $15,094; at 80 it is 20.2 and the same balance requires $19,802. The denominator falls every year, so the required share of the account rises from under 4% at 73 to 5% at 80 and 10% at 93.
Publication 590-B's own example: a $100,000 balance, owner turning 75, denominator 24.6, which gives an RMD of $4,065. The calculator reproduces it.
When you must start
The starting age moved twice under the SECURE Acts. If you were born in 1951 through 1959 your first RMD year is the year you turn 73. If you were born in 1960 or later it is the year you turn 75. (A 1959 birth year technically fits both clauses of the statute; the calculator uses 73 and flags it.) The first RMD can be delayed until April 1 of the following year; every later one is due by December 31. Delaying the first one means two RMDs are taxed in the same year, which is rarely a good trade.
Which accounts, and which table
Traditional, SEP and SIMPLE IRAs and employer plans such as a 401(k) or 403(b) all have RMDs. Roth IRAs and designated Roth accounts do not require withdrawals during the owner's lifetime. Each IRA's RMD is computed separately, but the total can be taken from any one or more of them; a 401(k)'s RMD must come from that plan, and if you are still working past the starting age a current employer's plan may let you wait.
The Uniform Lifetime Table is the default. If your spouse is the sole beneficiary of the account and more than ten years younger than you, the Joint Life and Last Survivor Table applies instead, and its larger denominator produces a smaller RMD: 25.3 rather than 24.6 for a 75-year-old with a 64-year-old spouse in the publication's example. That table is two-dimensional and is not built into this calculator; it tells you the Uniform figure is an upper bound and to have the joint figure checked.
The penalty for missing it
An RMD not taken by the deadline is subject to an excise tax of 25% of the shortfall, reduced to 10% if you correct it within two years, reported on Form 5329. Before 2023 the penalty was 50%. The IRS can waive it for reasonable cause when you have already taken the missed amount and ask.
The tax on the withdrawal
An RMD is ordinary income. The calculator stacks it on top of the other income you enter and runs the brackets twice, so you see the tax on the RMD itself rather than an average rate. Because it also raises the "combined income" that decides how much of your Social Security is taxable, a retiree in the 12% bracket can pay an effective 22% on each RMD dollar. The Social Security tax calculator shows that interaction, and a Roth conversion in the years before the starting age is the usual way to shrink future RMDs. A qualified charitable distribution (up to the annual limit, from an IRA, after 70½) satisfies the RMD without adding to income; it is not modeled here.
Official sources used on this page
- Publication 590-B (2025), Distributions from IRAs: Appendix B Table III (Uniform Lifetime) and the worked examples: 2025
- IRS: Retirement plan and IRA required minimum distributions FAQs (deadlines, 25% / 10% excise tax, Roth accounts, aggregation): 29-Jan-2026
- 26 U.S.C. 401(a)(9)(C): required beginning date and applicable age (73 / 75): page read 3 Sep 2026
- Rev. Proc. 2025-32 (2026 brackets and standard deduction used for the tax estimate): 2025-10-09
Every rule record names its source, revision and the date it was last verified; the results panel prints the ones your calculation used. Rules last verified 2 September 2026.